and, how about to-day's " brakes' " exposure to the elements? Is it better or
worse from the standpoint of "recovery" from exposure?
Not sure exactly what you mean. Steel rotors rust. High chrome stainless steel rotors dont normally rust, although salt will play hell with stainless.
A steel rotor with a little surface rust will be right back to normal after a little use. Scored rotors, of any type, begin to lose efficiency, dependent upon the damage.
Corrosion of the INTERIOR parts of the brake system can be an expensive problem. Even stainless steel can and will corrode, internally within the braking system as well as externally on the rotor.
If you maintain your braking system to minimize internal corrosion, you normally only have to spring for a pad replacement and possibly a rotor truing occasionally. Cheap.
But screw up a high performance system like a Teves, and you may find yourself up someones tailpipe (expensive), or at least having some VERY expensive repairs.